Fan

ABSTRACT

The invention relates to a fan for producing a fluid flow, particularly an air flow.  
     The problem of the invention is to provide a fan for a heatable fluid flow, in which the necessary energy consumption is reduced.  
     A fan according to the invention has an impeller, which has at least one blade for delivering the fluid. On at least part of the blades of the fan impeller is provided at least one heating element used for heating the fluid during the delivery operation of the fan.

[0001] The invention relates to a fan for producing a fluid flow,particularly an air flow.

[0002] Fans for producing a fluid flow, particularly an air flow, areused in numerous different ways. Such fans have an impeller and at leastone blade constructed or placed thereon for delivering the fluid. Inprinciple, such fans are generally known in the form of radial-flow fansand axial-flow fans. In the case of radial-flow fans the blades producean air flow, which is directed radially away from the rotation axis ofthe radial-flow fan and diverted in an outflow direction by the casingsurrounding the fan and which is oriented at right angles to therotation axis of the fan. In the case of axial-flow fans a fluid flow isproduced in the direction of the fan rotation axis.

[0003] Such fans are more particularly used for the delivery of gaseousfluids, particularly air. Such fans are also able to deliver liquidmedia.

[0004] Applications arise where the delivered fluid is not onlydelivered, but also has to be heated. The heating of the delivered fluidconventionally takes place by means of one or more heating elementspositioned behind the fan. For monitoring the temperature a temperaturesensor is positioned in general behind the heating element and by meansthereof the fan performance and/or heating capacity of the heatingelement are matched to one another in such a way that the conveyed fluidtemperature can be controlled or regulated.

[0005] It is a disadvantage of such constructions that the heatingelement following the fan represents a flow resistance for the fluidflow. Thus, the delivery rate of the fan must be made higher than wouldbe necessary for purely delivering the fluid. In addition, followingheating elements suffer from the disadvantage that as a result of theirfunction as a flow resistance and as a fixed, flowed-round component,impurities contained in the fluid can be deposited thereon. If the fluidis air, then frequently dust particles are deposited on the heatingelements. Into said dust particles can be incorporated impurities of theair, such as e.g. grease and water vapours. This is undesired forreasons of the delivery rate, heating element efficiency and hygiene.

[0006] The problem of the invention is to provide a fan for a heatablefluid flow, where the necessary energy consumption is reduced.

[0007] On the basis of the prior art features, this problem is solved bya fan having the characterizing features of claim 1. A fan according tothe invention has an impeller with at least one blade for delivering thefluid. At least one heating element is provided on at least one part ofthe fan impeller blades. The heating element is used for heating thefluid during the delivery operation of the fan.

[0008] According to a preferred development the heating elements areconstructed as a electrical heating elements and they are preferablychosen from the group composed of thick films, strip heaters andelectrically conductive ceramics.

[0009] Preference is given to constructions in which the heatingelements are located on the surface of the blades. It is particularlyadvantageous for the heating elements to be placed in heating elementchannels constructed on the blade side. It is also advantageous for theheating elements to be constructed in such a way that they supplementthe blades of a projection-free, smooth surface contour.

[0010] Preference is also given to constructions in which the heatingelements are positioned roughly along and parallel to the leading bladeedge in the rotor rotation direction. It is also advantageous if theheating elements extend over at least virtually the entire linearextension of the blades.

[0011] It is also advantageous if there is a temperature sensor at leaston part of the blades. Preferably the temperature sensor controls orregulates the heating capacity of heating elements, so that thetemperature of the delivered air is controlled or regulated. Accordingto a preferred development the temperature sensor, considered in theblade rotation direction, is positioned behind an optionally presentheating element. According to another advantageous development of theinvention temperature sensors are placed on blades having at least oneheating element.

[0012] According to a preferred development of the invention the heatingconductors or heaters are combined into at least two groups, the heatingcapacity being controlled or regulated by the optionally also timedswitching on or off of heater groups. According to a preferreddevelopment of the invention heaters of one blade are associated withthe same group. According to a further extending, advantageousdevelopment of the invention it is possible for the heaters of one groupto be arranged in a mutual parallel connection. In this and also otherconstructions of parallel-connected heaters, it is advantageousaccording to the invention if each of the heaters has a blow-out fuseassociated therewith to prevent excessive heating.

[0013] According to alternative developments of the invention the fancan be both an axial-flow fan and a radial-flow fan. In the case of aradial-flow fan it is possible for electrical contacting to take placein that the blades with the heaters located thereon to produce theelectrical connection between the two impellers of the radial-flow fanand are consequently supplemented to form circuits. It is in generalterms possible for the blades of the fan, which have a heating element,to be formed from a basic structure, a thick film heating elementenveloping said basic structure and the outer, laminar material filmforms the blade surface.

[0014] A preferred use of such a fan occurs in domestic appliances suchas (hot air) baking ovens or spin/tumbler dryers. A use is also possiblein other electrical appliances such as e.g. hair dryers, hand dryers,etc. Further applications can e.g. exist in blowers, particularly inmotor vehicles, as well as in (vane) pumps. All that is important isthat the fan delivers a fluid, which is simultaneously heatable.

[0015] The aforementioned and further features can be gathered from theclaims, the description and the drawings and the individual features,both singly or in the form of subcombinations, can be implemented in anembodiment of the invention and in other fields and can representadvantageous, independently protectable constructions for whichprotection is hereby claimed.

[0016] The invention is further described relative to embodiments shownin the attached drawings, wherein represent:

[0017]FIG. 1 Diagrammatically an axial-flow fan according to theinvention.

[0018]FIG. 2 Diagrammatically a radial-flow fan according to theinvention.

[0019]FIG. 1 diagrammatically shows an axial-flow fan according to theinvention.

[0020] It is possible to see a fan 11, which is constituted by acentrally positioned impeller 12 drivable by a not shown drive and fourblades 13 arranged in rotationally symmetrical manner with respect tothe centre of the impeller 12. The blades 13 can be convex or flat, e.g.sheet metal and in particular punched or stamped blades, which inconnection with the delivery of the fluid have a surface set about arotation axis 14 with respect to the rotation plane of the fan 11.Alternatively the blades 13 can have a complicated construction andwhich have been optimized with respect to their delivery rate at aspecific speed. The laminar design of the blades is independent of theimplementation of the invention.

[0021] On part or, as shown, on each of the blades can be located aheating element, e.g. a thick film heater 15. If the blade 13 comprisesa punched or stamped metal plate, initially an insulating layer and thenthe thick film heater 15 is applied to the plate surface. It is possibleto use conventional coating procedures used in this connection. Thepower supply is selected in such a way that there is a closed currentpath on a blade and in the vicinity of the mounting support of the blade13 is contacted with the impeller 12. Contacting can be brought about byconventional means such as the soldering of the contacts, whilst it isalso possible to provide clamping connections, which are automaticallycontacted on fixing the blades 13 to the impeller 12.

[0022] A temperature sensor 16 is also located in the centre of theblade 13 and is surrounded by the thick film heater loop 15 and is alsocontacted in the vicinity of the impeller 12. The signals and measuredvalues of the temperature sensor 16 can be used for controlling andregulating the performance and speed of the fan.

[0023] The contacting of the impeller with fixed components located onthe fan casing can e.g. take place by means of conventional brushcontacts or via inductively operating couplings.

[0024] To ensure that the fluid flowing past the blades 13 has a goodcontact with the thick film heater 15, the latter is preferably locatedon the side of the blade 13 which is exposed to the more powerful fluidflow, i.e. the front side considered in the fan rotation direction.

[0025] To control or regulate the heating capacity, it can beadvantageous to combine the heaters into groups. For example the twoheaters can be associated with facing blades of a group, which arealways switched on or off together. The heating capacity of the fan isthen influenced through the number of switched on groups. It is possiblewithin a single group to wire the heaters 15 in parallel. If then one ofthe heaters is damaged with a corresponding circuit interruption, theother heater in the group remains intact. Thus, in the present case twogroups of heaters could be formed and in the case of the operation ofonly a single heater group, roughly half the maximum possible heatingcapacity would be available. Through a correspondingly timed operationof the heaters there can be a virtually continuous regulation of thepower or capacity up to the maximum possible level.

[0026]FIG. 2 diagrammatically shows a radial-flow fan 11.

[0027] The fan 11 rotates about rotation axis 14 in the fan casing. Inthe vicinity of the rotation axis 14 can be provided correspondingcontacts, particularly brush sliding contacts, for contacting electriclines and for closing circuits. The blades 13 extend parallel to therotation axis 14 between the two impellers 12. The surfaces of theblades 13, which can once again be planar or convex, are inclinedslightly with respect to the radial orientation, so that medium isconveyed.

[0028] The blades 13 can be manufactured from a structure, which is e.g.a plastic injection moulding. During the injection moulding of thestructure it is possible to simultaneously injection mould round theheating element ends and/or metal punched grids, which are used for theelectrical connection of the individual heating elements and forcontacting with the power supply (insert technology). The heatingelement 15 extends over the entire length of a blade 13. The temperaturesensor 16 extends parallel to the heating element 15 and is locatedbehind it in the fluid flow direction.

[0029] The structure of the blade 13 can have recesses for the heater 15and temperature sensor 16, so that following the introduction orapplication of the heater and the temperature sensor there is a closed,smooth blade surface. It is also possible for the structure to be chosenin such a way that the blades are first supplemented by the heaters 15and optionally by the temperature sensor 16, which have the function andoperation of a closed blade, i.e. the structure is wholly or zonallyenveloped by heaters 15 and/or temperature sensors 16.

[0030] If the heater extends over the entire length of a blade, thesimplest situation is if it is contacted on both sides with the impeller12. If, with the exception of specific line portions intended for thispurpose, the rotation axis or pivot 14 is non-conductively constructedand consequently the two impellers 12 are isolated, it is easiest forthe contacting and power supply to take place from one side of the fanto the other and consequently the circuit is supplemented by the heatingelement 15 to form a closed circuit.

[0031] As shown in the drawings, it is not necessary for all the blades13 to have a heater 15 and/or a temperature sensor 16. It is also notnecessary for all the blades 13, which have a heater 15, to have atemperature sensor 16. It is also conceivable for a blade 13 to have atemperature sensor 16, although said blade 13 has no heater 15.

[0032] As explained relative to FIG. 1, it is possible to combine theheaters 15 into groups and within a group the heaters are preferablyconnected in parallel. As a result of the then possible stepwiseswitching on of individual groups, a stepped control/regulation of thefan heating capacity is possible.

[0033] The electrical contacting of the impeller 12 can e.g. take placeby means of a slip ring 17 and casing-side carbon brushes runningthereon. From the slip ring 17 the current is supplied by means of anelectrical line 18, which is mainly radially directed and whichsimultaneously can incorporate a distributor ring for the power supplyto several blades 13, is supplied to at least one blade 13, which has aheating element 15 extending over the entire width of a blade. On theother side of the blade 13 once again an electrical line 18 and a slipring 17 returns the current to the other side of the casing and fromthere back to the power supply, so that a closed circuit is obtained.

[0034] Alternatively to the use of a thick film heater it is possible touse a strip heater or some other electrical heater on the surface of ablade. It is particularly easy to produce a strip heater positionedbetween the two impellers 12 of the radial-flow fan 11.

[0035] In the case of all the embodiments it is possible to so dimensionthe heater 15 in at least one heating area thereof in such a way that itburns out when there is an excess temperature at said point andconsequently the circuit is interrupted. This reliably prevents aninadmissible overheating of the heater. If the other heaters arearranged in parallel and not in series to said heater, their function isnot impaired as a result of this.

1. Fan, with an impeller and at least one blade for delivering a fluid,wherein at least one heating element (15) for heating the deliveredfluid is provided on at least one part of the blades (13).
 2. Fanaccording to claim 1, wherein heating elements (15) are constructed aselectrical heating elements and are chosen from the group of thick filmheaters, strip heaters and electrically conductive ceramics.
 3. Fanaccording to claim 1, wherein heaters (15) are placed on the surface ofthe blades (13).
 4. Fan according to claim 3, wherein the heatingelements (15) are located in heating element channels constructed on theblade side.
 5. Fan according to claim 1, wherein the heating elements(15) are constructed in such a way that they supplement the blades (13)so that a projection-free, smooth surface contour is formed.
 6. Fanaccording to claim 1, wherein the heating elements (15) are placedroughly along and parallel to the leading edge of the blades (13) in therotor rotation direction.
 7. Fan according to claim 1, wherein atemperature sensor (16) is placed on at least part of the blades (13).8. Fan according to claim 7, wherein, considered in the blade rotationdirection, the temperature sensor (16) is placed behind a heatingelement (15).
 9. Fan according to claim 7, wherein the temperaturesensors (16) are placed on blades (13) having at least one heatingelement (15).
 10. Fan according to claim 1, wherein the heaters arecombined into at least two groups, the heating capacity preferably beingcontrolled or regulated by switching on or off groups of heaters (15).11. Fan according to claim 10, wherein the heaters (15) of a blade (13)are associated within the same group.
 12. Fan according to claim 1,wherein it is part of an axial-flow fan.
 13. Fan according to one of theclaim 1, wherein it is part of a radial-flow fan.
 14. Fan according toclaim 13, wherein the electrical contacting of the heaters (15) takesplace in that blades (13) with heaters (15) located thereon produce anelectrical connection between two impellers (12) of the radial-flow fanand consequently are supplemented to form circuits.
 15. Fan according toclaims 13, wherein blades (13) comprise a base structure, which at leastzonally is coated with a thick film heating element.
 16. Use of a fanaccording to claim 1 in a domestic appliance.
 17. Use of a fan accordingto claims 1 in a device of the group composed of baking ofen,particularly a hot air baking oven, spin/tumbler dryer, hand dryer. 18.Use of a fan according to claim 1 in vane pumps and blowers in motorvehicles.